AD FS Development
Developers can use the Active Directory Federation Services (AD FS) SDK to customize and extend the capabilities of AD FS.
Customizing Client Logon and Home Realm Discovery Pages discusses how to customize the look of the ASP.NET pages exposed in your AD FS implementation.
System.Web.Security.SingleSignOn
System.Web.Security.SingleSignOn.Authorization
Active Directory Federation Services Overview
AD FS TechCenter
AD FS Documentation Blog
ADFS Product Support blog